Yarnlike product kept together by circumjacent polymer material, and a method and an apparatus for producing said product

ABSTRACT

A generally twistless yarnlike product is kept coherent by means of circumjacent polymer rings applied at intervals, high bulk being achieved by a loop effect as the filaments or fibres are differently contracted between the rings. To make such a product and similar products bound with rings, a bunch of fibres or filaments is temporarily brought in twisted and revolving state, and strips of a polymer in fluid state are spun around by means of the revolution of the bunch.

9 lllied States Patent 1 1 11 1 3,762,142

Rasmussen 1 1 Oct. 2, 1973 1 1 YARNLIKE PRODUCT KEPT TOGETHER [56] References Cited MATERIAL AND A METHOD AND AN 3,116,588 1/1964 Breen et a1 57/140 R APPARATUS FOR PRODUCING 3,388,025 6/1968 DricaMinieris ct a1. 156/441 PRODUCT 3,434,275 3/1969 Backers ct a1. 57/139 Inventor: le Bendl RaSmuSSemTOPStykkeL-I, 3,446,002 /1969 K1ppan 57/140 R Copenhagen, Denmark Primary ExaminerWerner H. Schroeder 1221 Flled: 1971 Attorney-William .1. Daniel [21] Appl. No.: 120,186

[57] ABSTRACT 1 1 Foreign Application Priority Data A generally twistless yarnlike product is kept coherent Mar. 3, 1970 Denmark 1040/ b means of circumjacent polymer rings applied at in- Apr. 2, 1970 Denmark 1 4/7 tervals, high bulk being achieved by a loop effect as the filaments 0r fibres are differently contracted between 1 57/34 57/l57 the rings. To make such a product and similar products 57/34 T bound with rings, a bunch of fibres or filaments is tem- [51] Int. Cl DOZg 3/00, DOZg 3/40 porarily brought in twisted and revolving State, and [58] Field of Search 57/11, 12, 13, 18, strips of a polymer in fluid state are spun around by 57/34, R, 140 BY, 157 R, 157 TS, 160, 157 MS; 156/434, 441, 167; 264/103, 167, 174

means of the revolution of the bunch.

15 Claims, 5 Drawing Figures PATENTEU w fem:

SHEET 2 BF 2 YARNLIKE PRODUCT KEPT TOGETHER BY CIRCUMJACENT POLYMER MATERIAL, AND A METHOD AND AN APPARATUS FOR PRODUCING SAID PRODUCT Yarns or yarnlike products are known which are kept together through a binding material instead of through twisting. These products are, however, either relatively stiff and compact, or they show little coherency, and their applications are therefore limited. The present invention aims at obtaining an adequate combination of volume, flexibility, resilience, and coherency.

It is known to extrude a bundle of filaments which are thereupon entwined with a thread of molten polymer from a nozzle rotating around the bundle, whereby without actual twisting a yarn or yarnlike product is obtained with a structure simulating a twist.

The present invention likewise relates to a yarn or yarnlike product consisting of filamentitious structures, kept in bunched relationship by means of a circumjacent polymer material and to a method and an apparatus for producing said yarn or yarnlike structure. The characteristical features of the yarn or yarnlike product according to the invention are that said circumjacent polymer material forms rings which keep the bunch in a compact round shape within short zones, the intervening zones of the bunch being in a bulky state.

Due to the segmental arrangement where zones of strong binding alternate with zones without any direct binding all the above-mentioned properties can be obtained at the same time. The rings should preferably, but not necessarily, be adhesively bonded to the circumferential portion of the bunch.

The lengths of the zones supplied with rings should for most purposes be in a range between about 0.2 mm and 1 cm, while the lengths of the intervening zones should for most purposes be in a range between about l mm and 5 cm. Dependent on the use, the bunch can consist of filaments and/or staple fibres and/or fibrillated film and/or non-fibrillated, transversely compacted film and/or of ribbons and/or other fibrelike or filamentlike structures. The product can further be a single, transversely compacted film kept in the shape of a bunch by means of the rings.

An advantageous embodiment of the product according to the invention is characterized in that the filamentitious structures in each intervening zone have different lengths measured from ring to ring in the unloaded condition of the yearn. This is generally obtained by different shrinkage of the filamentitious structures after the application of the rings, as will be explained below. The relatively long fibres will be bent and will thereby tend to elongate the product, while the relatively short fibres will be straightened out and will tend to contract the length. There is hereby obtained a high and very stable volume.

An embodiment of the product according to the invention, of the type which comprises different lengths between the rings, is further characterized in that said lengths are shorter in the central portion of the bunch and longer in the outer portion of the bunch. Because of the order of this structure there is thereby obtained the most pronounced visual effect of the structure and generally also the highest volume.

An alternative embodiment, also of the type which comprises different lengths between the rings, is characterized in that the distribution of the shorter and the longer filamentitious structures is at random. Although this arrangement generally produces a somewhat lower volume, the bulk is on the other hand generally more stable.

The random distribution can be obtained by blending staple fibres of different ability to shrink and making a raw-yarn herefrom in conventional manner. Another way to obtain random distribution is to lay two network-formed, fibrillated films from different substances one upon the other and compact the plied structure transversely.

It has been mentioned that the longer filamentitious structures and the shorter ones generally represent different amounts of shrinkage, and these differences can be obtained by a variety of selections.

Thus in one embodiment the shorter filamentitious structures consist of an elastomer, and the longer ones consist of a stiffer substance. This selection has the advantage that the elastic material easily elongates until the elongation is stopped by the straightening-out of the stiffer filamentitious structures which will then provide a relatively high tensile strength. Further the elastomer will readily contract to the shorter length and thus the bulk will recover efficiently when the tension has been released. For apparel purposes and in other cases when fine fibres are generally required, the elastomer should preferably be a thermoplastic elastomer of the type where the stabilisation is due to crystalline segments instead of real cross-linking, as for example extrudable polyurethane rubber.

In another embodiment the shorter filamentitious structures are crimped bicomponent fibres or filaments, and the lower filamentitious structures are mono-component fibres or filaments. Crimped bicomponent fibres generally act like elastomer fibres and have the advantage that they are much easier to blend with other fibres (generally in uncrimped state), and the choise of applicable substances is wider. On the other hand, the tension in stretched state at low elongations is generally lower.

When distinguishing between shorter and longer filamentitious structures in the cases when some of the fibres are curled-up bicomponent fibres, what matters is, of course, not the lengths along the helices, but the lengths measured along the axes of the helices.

In still another embodiment the filamentitious structures are bicomponent fibres of different crimp. In this manner the product has particularly high extensability, but on account to some extent of the volume.

Cut up to short lengths the product of the invention can with advantage be used as an artificial feather or down, e.g. in pillows and quilts. In order to fit well to the shape of the body, the lengths should preferably be as short as possible in proportion to the transverse span, and for this and similar purposes an embodiment of the product is characterized in that it only comprises two rings.

Though the transverse coherency in the yarn or the yarnlike product is substantially due to the rings, it should be understood that the product may also be provided with a slight twist.

The invention further comprises a method for binding a bunch of filamentitious structures with rings at intervals. The method is characterized by subjecting the bunch of filamentitious structures to a false-twist process so as to temporarily bring it in twisted and revolving condition, and supplying a fluid polymer spotwise while the bunch is in said condition, the supply being maintained during not less than one revolution of the twisted bunch, hereby carrying the site of supply foreward substantially at the same velocity and in the same direction as the bunch, and solidifying the polymer.

As it appears from the foregoing an object of this method is to provide for a production of yarn or yarnlike products with a special combination of advantageous properties. A further object, however, is to establish the transversal coherency in a yarn or yarnlike structure by a particularly fast and practical process. It has proven that the method of the invention can be carried out many times faster than real twisting and also essentially faster than the method mentioned in the introduction, i.e. the method of entwining a bunch of filaments with a helice of molten polymer from a nozzle revolving around the bunch. False-twist, as wellknown, can be carried out very fast, and it has proven that the spotwise application and the solification of a fluid polymer can be carried out at similar velocities.

False-twist operations, as known, are normally used for the production of crepe yarns, as the deformations in each fibre are fixed thermically in the twisted condition. The present invention does, however, not specifically aim at producing crepe yarn, and such a fixation is consequently not essential for the exercise of the method.

The false-twist process may be executed by use of several methods which are well-known as such, but especially high speed and the advantage in working under high tension is obtained when the said false-twisting of the yarn or the yarnlike product takes place by rolling in a substantially linear zone between two friction members, of which at least one comprises two or several friction elements which are successively brought into contact with the other friction member, whereas the friction elements during the contact with the opposite friction member are displaced transversely to the travelling direction of the yarn and displaced back to the starting point when the contact ends. The use of such a method for rolling yarn is in another connection described in Plastics Rubbers, Jan. 1970, page 31.

The polymer to form the rings can be supplied either in molten or dissolved or emulsified state, or in form of one or several prepolymers. correspondingly the solidification can take place either by cooling or by evaporation of a solvent or of an emulsifier, or by coagulation of the emulsion, or by curing of the prepolymer(s).

In an embodiment of the method according to the invention, the supply is carried out by means of an endless row of small reservoirs for the polymer which are in repeated succession bi'ought into contact with the revolving bunch, carried along herewith, and brought out of contact again. Due to the continuous movements this embodiment is particularly fast.

The most expedient manner of feeding each of said reservoirs is by extrusion through an extrusion channel ending in the reservoir. (The reservoirs can simply be the orifices of the channels). An alternative manner of feeding the reservoirs is by means of a doctors knife or likewise.

Another embodiemnt of the method according to the invention is characterized in that the fluid polymer is supplied by means of nozzles which during the spinning-around process are moved foreward together with the yarn at the same velocity as this, whereupon the nozzles are brought back to the starting point, preferably at a velocity which is substantially higher than that of the yarn. This embodiment is somewhat slower, but enables a particularly precise dossage of the polymer. There will generally be drawn a thin thread of the polymer between the rings.

The method of the invention can be used to produce the above-mentioned product of particularly high bulk. For this purpose an embodiment is characterized in that the filamentitious structures are oriented by stretching before the supply of the polymer and maintained oriented during the supply, and that subsequent to said supply different dilamentitious structures are subjected to different shrinkage to develop a bulk. The best results are obtained by use of filamentitious structures from different substances which exhibit different tendencies to shrinkage. The substances need not be from chemically different polymers, but may be from the same polymer but in different grades.

However, it is also possible to cause the different shrinkage by uneven heating (and/or swelling) of dif ferent portions of the bunch.

The invention further relates to an apparatus for binding a bunch of filamentitious structures by rings at intervals. The apparatus comprises, in combination, means to subject a bunch of filamentitious structures to temporary twisting and revolution and in immediate succession hereto to untwisting and elimination of the revolution, means to supply a fluid polymer spotwise to the bunch at the station where the bunch is twisted and revolving, and to maintain the supply during at least one revolution of the bunch and to advance the site of supply at substantially the same velocity and in the same direction as the bunch, and means to solidify the polymer.

To obtain continuous movements, an embodiment of said apparatus is characterized in that said supply means consist of a roller with a ring-formed row of cavities at the surface, means to feed the polymer into said cavities, means to rotate said roller at substantially the same circumferential velocity as the velocity of the bunch and means to guide the bunch into contact with cavities.

A very expedient feed of the polymer is obtained when said roller is an extrusion die supplied with channels to feed each of said cavities from inside.

The invention will hereafter be described in further detail with reference to the drawings, of which FIG. 1 is a photo showing in 4 times magnification a yarn of the invention bound with rings and consisting of 'bicomponent crimped fibres which are of different lengths between the rings,

FIG. 2 is a schematical representation of the preferred embodiment of the product where the filamentitious structures have different lengths between the rings,

FIG. 3 shows, in perspective and schematical view, a process line for binding a bunch with rings at intervals,

FIG. 4 shown in longitudinal view, is a detail of the extruder die for the spotwise supply of polymer in the line of FIG. 3,

FIG. 5 is a transverse section along II of FIG. 4

In FIG. 2 a bunch of many filaments or staple fibres are bound together by the ring-formed entwined polymer strips 1, 2, and 3, which form rings. The filaments or staple fibres, 4, 5, 6, and 7 are comparatively long, as measured from one edge of a ring to the adjacent edge of an adjacent ring. These long filaments or fibres form a kind of loops and tend to elongate the entire bunch, while the more contracted filaments or staple fibres, 8 and 9, tend to make the entire bunch shorter. For the sake of clarity, the rest of the filaments, e.g. 10, are only indicated as whiskers in the immediate neighbourhood of the rings, but should be understood as generally occuplying the entire zone between adjacent rings with no or relatively few loose ends. Some of these filaments or fibres, which are only partly shown, should be relatively long, and others relatively short. Of course, it is also possible to use a range of many different lengths in each intervening zone.

The filaments or fibres, 8 and 9, are shown as really straightened out, but could also be of helical configuration as obtained by shrinkage of conjugently spun filaments or fibres from two components in side-by-side relationship. (Each filament or fibre will then alternate between left-turning and right-turning helices). In similar manner, the loop-forming filaments or fibres, 4, 5, 6, and 7 can also be of helical configuration although they must of course be less contracted than 8 and 9.

Due to the loop-effect the structure exhibits, as it has proven, a high and resilient bulk. Furthermore, the firm binding at intervals provides for a high resilience in respect of bending of the yarnlike product.

In FIG. 3 a twistless raw-yarn or similar, 11, is shown taken from a bobbin, 12, but could of course be taken directly from a card or an extrusion device. 11 can be any kind of raw-yarn or similar, even a single, relatively narrow film. From a set of driven feed rollers, 13 14, and 15 the yarn is fed into a zone where it is kept in twisted and revolving condition by means of a falsetwist device consisting of the section-formed, driven rollers, 16 and 17. These rollers rotate as shown by the arrows, 18 and 19, and at the same time each section, when passing the nip. is moved at a constant velocity in the directions shown by the arrows, 20 and 21, respectively, i.e. the two rollers, 16 and 17 constantly act in different directions on the yarn, hereby producing a false-twist. Having passed the nip, each section is reverted to be ready for the same twisting action when it again meets the nip. These reciprocations, syncronized with the rotations, are guided by a set of cam-devices. For a more detailed description of the false-twist rollers, see the article False Twist and Stretching Process for Tape," in Plastics Rubbers, January 22, 1970. This device is particularly fast, enables simultaneous treatment of many yarns, and a high tension in the zone of twist. It is of advantage to establish such a tension in order to overcome the friction from the supply means which counteract the revolution of the yarn.

In the zone between the feed-rollers, 14-15, and the section-formed rollers, 16-17, the yarn, here numbered 22, will be in twisted and revolving condition, but having left the section-formed rollers, 14-15, the yarn, here numbered 23, will again be twistless. The application of the rings, 24, is carried out by means of a kind of printing roller, 25, which is rotated so as to follow the advance of the yarn, 22. This printing roller, however. is also an extrusion die, see the more detailed FIG. 4 and 5. The molten polymer is fed from the extruder 26, through a fitting 27, and into a central die part, 28, which does not follow the rotation of 25.

For the sake of clarity, FIG. 3 only shows the processing of one yarn, but in actual fact several yarns should be processed simultaneously, as it also appears from the construction in FIG. 4.

In order to distribute the molten polymer between the different yarns, the central die part, 28, houses a distribution chamber, 29, supplied with a number of slots, 30, which are evenly distributed along the length of the printing roller. Each slot, 30, feeds an array of radial channels, 31, in the rotating roller, 25, each array of channels terminating in a circular row of orifices from which is printing takes place. There is sealing between the fixed central die part 28, and the rotating roller, 25, and the extrusion through each channel, 31, takes place in pulsations when the orifice is in the position for printing.

In order to ensure a smooth distribution of the polymer in each spot, each row of orifices is placed at the bottom of a semi-cylindrical groove, 32, the diametre of which is only slightly bigger than the diametre of the twisted yarn, 22. The resistance against the revolution of the yarn is minimalized by only letting the yarn contact the printing roller" over a short distance, however long enough to make the yarn turn not less than one revolution around itself during the contact in order to form a well-shaped ring.

To obtain this it is furthermore essential to rotate the printing roller" at such a speed that the orifices exactly or almost exactly follow the advance of the yarn. For the sake of clarity, the drive is not really shown, but only indicated by the arrow, 33.

Further, the die is heated for the extrusion, but the heating elements are not shown. Neither are shown the thread guides before the feed roller, 13, and before the printing roller," 25, which keep the different yarns spaced apart and ensure a safe guiding of the yarns to the grooves, 32.

Between the printing roller, 25, and the false-twist rollers, 16 and 17, the rings, 24, are strongly cooled by means of a water spray or a water bath (not shown). A cooling bath, however, must be so constructed that any substantial hindrance against the revolution of the yarn, 22, is avoided.

To avoid squeezing of the rings, the section-formed rollers, 16, and 17, must be coated with soft rubber, or a more practical measure is to supply one or both surfaces with grooves which are spaced at the same distance from one another as the distance between the rings, 24, at the same time as the printing roller, 25, and the false-twist rollers, 16 and 17, are syncronized in such manner that the rings, 24, will fit into said grooves and a squeezing of the rings hereby will be prevented.

After the false-twist rollers, 16 and 17, follows a set of driven pull-rollers, 36 and 37, which assist the falsetwist rollers, 16 and 17, in setting-up a tension in the yarn, 22, while the latter is guided in revolving state over the printing roller", 25. As already mentioned, this tension is set-up to overcome the resistance against said revolution.

If the raw-yarn, 11 consists of filaments, fibres or other filamentitious structures of different substances, and if there is established a high tension before and/or during the false-twist, then there will generally spontaneously develop a bulk when the tension is released in twistless state. This is indicated at 34 before the spooling on the bobbin, 35, and is due to different shrinkage of the different substances. To further promote such different shrinkage, an oven can be provided for in the line after the rollers, 36 and 37, but a heat treatment to develop the bulk can of course also be carried out during respooling of the yarn or in the final textile product.

To produce short lengths for use as feather or down substitute, the bobbin, 35, is substituted by a cutting device, which is syncronized with the printing roller," so as to cut regularly between the rings.

Yarnlike products manufactured according to the invention may be applied for a great variety of textile and technical purposes, and the applications range from the highest fineness used of yarn, i.e. about 20 denier, to the coarest yarn, i.e. about 100 denier, with preference, however, for the range from about 500 denier to about 30.000 denier. The examples below illustrate different applications.

EXAMPLE I This example illustrates the use of the invention to manufacture a bulked effect-yarn for curtains.

The raw-yarn consists of a bicomponent filaments from polypropylene and polycaprolactame bonded in sideby-side relationship by means of a thin layer of an ionomer polyethylene which exhibits adhesive properties. The raw-yarn is produced by the method and apparatus explained in the article Split Film Gets a Second Look, in Textile Industries," July 1969. Due to casual irregularities of the dieparts the fibres in the yarn exhibit different crimpability, after stretching, and the distribution of the differences is almost at random. The average fibre denier is about 20 and the yarn denier about 4.000.

By means of a laboratory line as shown in FIG. 3, short rings of polypropylene are applied at a mutual distance of 2 cm. The melt index of the polypropylene is according to ASTM D l238-62T, condition K. In order to obtain a smooth print" it has proven advantageous to use such a relatively low-viscous grade. The rings are cooled in a water bath. The false-twist is carried out with 6 turns per 10 em.

The bulk is developed by heating to 120C in relaxed state by which each of the filaments crimps in helical manner, but to different degrees. The look of th yarn is almost as shown in the photo, FIG. 1. The yarnlike structure is used as weft in a fabric with fine nylon threads as warp, thereby a very attractive visual effect is obtained.

EXAMPLE 2 This example illustrates the use of the invention to manufacture a feather substitute for filling of pillows or quilts.

For thispurpose the raw-yarn should be a carded blend of4 denier monocomponent polyethyleneterephthalate staple fibres and 4 denier bicomponent polyethyleneterephthalate staple fibres, again in a yarn, denier of about 4.000. The materials-for the rings should be a copolymer of polyethyleneterephthalate and polyethyleneglycol of melting point l80C and melt index 2 according to the same ASTM specification, but condition E. The rings-should be applied as thin and short as possible and at a spacing of 4 cm. After elimination of the twist the yarn should be cut between the rings to short lengths, each comprising 2 rings, and the bulk developed by heating.

EXAMPLE 3 This example illustrates the use of the invention to manufacture a grass substitute.

As raw-yarn is used two flat, network-formed webs, each formed by needle-fibrillation of oriented film. One is made from polypropylene and the other one from polycaprolactame. Each has an average fibre denier of about 50 and a yarn denier of about 2.000.

The two flat networks which are taken from two spools are assembled one on top of the other without any adhesion, and are fed into the line of FIG. 3. The polymer for the rings, and the process is the same as in example i, but by means of wider orifices the rings are made about 3 mm long, and the spacing between the rings is 1 cm.

The resulting product, after heat treatment at C, shows high resilience and a stable high bulk and is suitable as a tufting product for sport-fields, etc.

I claim:

1. A method of increasing the coherency of substantially twistless yarn which comprises advancing a substantially untwisted yarn formed of normally loose fibrous material from a supply source, temporarily compacting said normally loose advancing yarn at least localized regions successively spaced along its length, forming around the yarn while compacted at each of said localized regions a discrete continuous ring of solid polymer distinct from said fibrous material, said rings tightly embracing the yarn in said compacted condition, releasing said yarn from said compaction, and collecting the ringed yarn thus obtained.

2. The method of claim 1 wherein said yarn is temporarily compacted by inserting false twist therein, said rings are formed while the yarn is in false twisted condition, and the false twist is removed after the rings are formed to release the yarn to its normal loose condition.

3. The method of claim 1 wherein said rings are spaced along said yarn at intervals from about 1 mm to 5 cm and are about 0.2 mm to 1 cm in thickness lengthwise of the yarn.

4. The method of claim 1 wherein said discrete polymer rings are formed by applying around the complete periphery of the compacted yarn at each of said localized regions a narrow band of liquid containing normally solid polymer in flowable condition and solidifying polymer to form said solid continuous polymer rings before releasing the yarn from said compacted condition.

5. The method of claim 4 wherein said polymer containing liquid is applied to said yarn from at least one applicator orifice and each such orifice is displaced in the lengthwise direction of the yarn at substantially the rate of yarn movement while the liquid is applied therefrom.

6. The method of claim 5 wherein twise is temporarily inserted in said yarn to compact the same and said orifice is displaced along a fixed path on one side of the yarn while the yarn is being temporarily twisted, said displacement being of a sufficient length that the yarn undergoes at least one revolution while the liquid is applied thereto from said orifice.

7. The method of claim 1 wherein said fibrous material comprises fibres having a differential capacity to shrink and the ringed yarn is treated to develop said shrinkage, thereby increasing the bulk of said yarn.

8. Apparatus for producing a coherent substantially twistless yarn comprising feed means for feeding said yarn along a determined path, liquid applicator means along said path for applying around the complete periphery of the yarn at each of a lengthwise succession of localized regions a discrete continuous narrow band of a liquid containing a normally solid polymer in flow able condition, and means for engaging said yarn to temporarily compact said yarn in at least said successive localized regions therealong to advance of said liquid applicator means, means for maintaining said yarn regions in said compact condition until said polymer band has solidified and then releasing said yarn from said compacted condition.

9. Apparatus as in claim 8 wherein said yarn engaging means comprises means for inserting false twist in said yarn situated downstream of said applicator means along the yarn path.

10. Apparatus as in claim 8 wherein said applicator means comprises a nozzle having at least one orifice, means for supplying said polymer-containing liquid to said nozzle, and means for displacing said nozzle orifice for a limited distance along the yarn path at substantially the rate of feed of said yarn.

11. Apparatus as in claim 10 comprising means for revolving said yarn around its axis while the nozzle orifice applies said polymer containing liquid to the yarn, and said nozzle is fixed against translation around said yarn, and said orifice is displaced with said yarn for a distance sufficient for the yarn to be revolved at least one revolution whereby a continuous band of polymer is formed.

12. Apparatus as in claim 11 wherein said nozzle has a plurality of spaced apart orifices moving in a continuous path having a stretch extending adjacent a limited section of the yarn path, and means for periodically supplying each orifice with polymer-containing liquid while the same is within said stretch.

13. Apparatus as in claim 8 wherein said applicator means comprises a rotatably supported roll having a plurality of radially extending ports spaced around the periphery thereof, and conduit means within said roll for supplying each port in succession with polymercontaining liquid through a limited arc of rotation, said roll being disposed for rotating contact with said yarn in registration with said ports.

14. Apparatus as in claim 13 wherein said roll has a peripheral groove intersecting said ports for receiving said yarn, and said yarn passes through a limited arc of said groove generally corresponding with the are over which the ports are supplied with polymer-containing liquid.

15. A method of producing a coherent substantially twistless yarn which comprises advancing from a supply source a twisted yarn formed of a plurality of fibrous structures, forming around such yarn at each of a lengthwise succession of closed spaced intervals a discrete continuous ring of solid polymer distinct from said fibrous structures and tightly embracing the yarn, and untwisting and collecting the ringed yarn thus obtained. 

1. A method of increasing the coherency of substantially twistless yarn which comprises advancing a substantially untwisted yarn formed of normally loose fibrous material from a supply source, temporarily compacting said normally loose advancing yarn at least localized regions successively spaced along its length, forming around the yarn while compacted at each of said localized regions a discrete continuous ring of solid polymer distinct from said fibrous material, said rings tightly embracing the yarn in said compacted condition, releasing said yarn from said compaction, and collecting the ringed yarn thus obtained.
 2. The method of claim 1 wherein said yarn is temporarily compacted by inserting false twist therein, said rings are formed while the yarn is in false twisted condition, and the false twist is removed after the rings are formed to release the yarn to its normal loose condition.
 3. The method of claim 1 wherein said rings are spaced along said yarn at intervals from about 1 mm to 5 cm and are about 0.2 mm to 1 cm in thickness lengthwise of the yarn.
 4. The method of claim 1 wherein said discrete polymer rings are formed by applying around the complete periphery of the compacted yarn at each of said localized regions a narrow band of liquid containing normally solid polymer in flowable condition and solidifying polymer to form said solid continuous polymer rings before releasing the yarn from said compacted condition.
 5. The method of claim 4 wherein said polymer containing liquid is applied to said yarn from at least one applicator orifice and each such orifice is displaced in the lengthwise direction of the yarn at substantially the rate of yarn movement while the liquid is applied therefrom.
 6. The method of claim 5 wheRein twise is temporarily inserted in said yarn to compact the same and said orifice is displaced along a fixed path on one side of the yarn while the yarn is being temporarily twisted, said displacement being of a sufficient length that the yarn undergoes at least one revolution while the liquid is applied thereto from said orifice.
 7. The method of claim 1 wherein said fibrous material comprises fibres having a differential capacity to shrink and the ringed yarn is treated to develop said shrinkage, thereby increasing the bulk of said yarn.
 8. Apparatus for producing a coherent substantially twistless yarn comprising feed means for feeding said yarn along a determined path, liquid applicator means along said path for applying around the complete periphery of the yarn at each of a lengthwise succession of localized regions a discrete continuous narrow band of a liquid containing a normally solid polymer in flowable condition, and means for engaging said yarn to temporarily compact said yarn in at least said successive localized regions therealong to advance of said liquid applicator means, means for maintaining said yarn regions in said compact condition until said polymer band has solidified and then releasing said yarn from said compacted condition.
 9. Apparatus as in claim 8 wherein said yarn engaging means comprises means for inserting false twist in said yarn situated downstream of said applicator means along the yarn path.
 10. Apparatus as in claim 8 wherein said applicator means comprises a nozzle having at least one orifice, means for supplying said polymer-containing liquid to said nozzle, and means for displacing said nozzle orifice for a limited distance along the yarn path at substantially the rate of feed of said yarn.
 11. Apparatus as in claim 10 comprising means for revolving said yarn around its axis while the nozzle orifice applies said polymer containing liquid to the yarn, and said nozzle is fixed against translation around said yarn, and said orifice is displaced with said yarn for a distance sufficient for the yarn to be revolved at least one revolution whereby a continuous band of polymer is formed.
 12. Apparatus as in claim 11 wherein said nozzle has a plurality of spaced apart orifices moving in a continuous path having a stretch extending adjacent a limited section of the yarn path, and means for periodically supplying each orifice with polymer-containing liquid while the same is within said stretch.
 13. Apparatus as in claim 8 wherein said applicator means comprises a rotatably supported roll having a plurality of radially extending ports spaced around the periphery thereof, and conduit means within said roll for supplying each port in succession with polymer-containing liquid through a limited arc of rotation, said roll being disposed for rotating contact with said yarn in registration with said ports.
 14. Apparatus as in claim 13 wherein said roll has a peripheral groove intersecting said ports for receiving said yarn, and said yarn passes through a limited arc of said groove generally corresponding with the arc over which the ports are supplied with polymer-containing liquid.
 15. A method of producing a coherent substantially twistless yarn which comprises advancing from a supply source a twisted yarn formed of a plurality of fibrous structures, forming around such yarn at each of a lengthwise succession of closed spaced intervals a discrete continuous ring of solid polymer distinct from said fibrous structures and tightly embracing the yarn, and untwisting and collecting the ringed yarn thus obtained. 